NCP5007SNT1 데이터 시트보기 (PDF) - ON Semiconductor

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NCP5007SNT1

Compact Backlight LED Boost Driver

ON Semiconductor 

NCP5007

Output Current Range Set−Up

The current regulation is achieved by means of an external sense resistor connected in series with the LED string.

Vbat

L1

22 mH

Vout

D1

4

FB

Q1

1

CONTROLLER

GND

R1

xW

Figure 8. Output Current Feedback

GND

The current flowing through the LED creates a voltage

drop across the sense resistor R1. The voltage drop is

constantly monitored internally, and maximum peak current

allowed in the inductor is set accordingly in order to keep

constant this voltage drop (and thus the current flowing

through the LED). For example, should one need a 10 mA

output current, the sense resistor should be sized according

to the following equation:

R1

+

Feedback Threshold

Iout

+

200 mV

10 mA

+

20

W

(eq. 9)

A standard 5% tolerance resistor, 22 W SMD device,

yields 9.09 mA, good enough to fulfill the back light

demand. The typical application schematic diagram is

provided in Figure 9.

Vbat

Pulse

GND

U1

3 EN

5

Vbat

C1

4.7 mF

L1

22 mH

GND

GND

2

GND

1

FB

Vout 4

NCP5007

D1

MBR0530

C2

1.0 mF

R1

22 W

D6 D5 D4 D3 D2

LED LED LED LED LED

GND

Figure 9. Basic Schematic Diagram

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